In a formation of an electro-photographic image, rotating bodies such as a photoconductor drum and a developing drum are driven. When a toner cartridge including the photoconductor drum is used, driving torque required for driving the toner cartridge is different depending on the specification of the toner cartridge. Therefore, a known technique is proposed in which information on the driving torque is stored in the toner cartridge and can be utilized for a printer.
The above-described technique realizes a driving control according to the driving torque required for driving a toner cartridge. However, the technique provides the driving control by merely outputting motor current values stored in association with the driving torque, without any consideration for a change in internal environments of an image forming apparatus due to the drive.